I thought we might have heard about this before, but I don’t see previous reports.
On what browsers/devices/versions does this occur on?
Some things you can try:
Make sure the video isn’t being scaled and try to export at a standard resolution (480p, 720p, 1080p etc.). At least make sure it isn’t exported with an odd numbered resolution
Try unchecking “Use WebKit graphics acceleration” and/or checking “Position with CSS left/top” in the Document Inspector
Disable any flexible layout if you are using that and see if that helps
Try exporting as a different codec and see if that makes a difference